A series of Cd(II) complexes with π–π stacking and hydrogen bonding interactions: Structural diversities by varying the ligands

Seven new Cd(II) complexes consisting of different phenanthroline derivatives and organic acid ligands, formulated as [Cd(PIP)2(dnba)2] (1), [Cd(PIP)(ox)]·H2O (2), [Cd(PIP)(1,4-bdc)(H2O)]·4H2O (3), [Cd(3-PIP)2(H2O)2]·4H2O (4), [Cd2(3-PIP)4(4,4′-bpdc)(H2O)2]·5H2O (5), [Cd(3-PIP)(nip)(H2O)]·H2O (6), [Cd2(TIP)4(4,4′-bpdc)(H2O)2]·3H2O (7) (PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 3-PIP=2-(3-pyridyl)imidazo[4,5-f]1,10-phenanthroline, TIP=2-(2-thienyl)imidazo[4,5-f]1,10-phenanthroline, Hdnba=3,5-dinitrobenzoic acid, H2ox=oxalic acid, 1,4-H2bdc=benzene-1,4-dicarboxylic acid, 4,4′-H2bpdc=biphenyl-4,4′-dicarboxylic acid, H2nip=5-nitroisophthalic acid) have been synthesized under hydrothermal conditions. Complexes 1 and 4 possess mononuclear structures; complexes 5 and 7 are isostructural and have dinuclear structures; complexes 2 and 3 feature 1D chain structures; complex 6 contains 1D double chain, which are further extended to a 3D supramolecular structure by π–π stacking and hydrogen bonding interactions. The N-donor ligands with extended π-system and organic acid ligands play a crucial role in the formation of the final supramolecular frameworks. Moreover, thermal properties and fluorescence of 1–7 are also investigated.